Wheel bearing devices comprising an outer member having raceways in double rows on its radially inner surface and fixed to a vehicle body, an inner member having raceways in double rows opposing to the respective raceways of the outer member on its radially outer surface and fixed to a wheel, and rolling elements disposed between the raceways of the inner and outer members include a wheel bearing device with a rotation sensor mounted on the inboard side to detect rotation of the wheel to control devices such as an ABS (Antilock Brake System). This rotation sensor basically consists of a magnetic encoder magnetized such that different magnetic poles are alternately arranged in the circumferential direction and mounted on the inner member, which is a rotating race, and a magnetic sensor mounted on the outer member, which is a fixed race, for detecting change of flux as the magnetic encoder rotates.
Such wheel bearings with a rotation sensor include one wherein an arcuate sensor holding portion is formed with its radially inner end protruding toward the inboard side and bent radially inward, on an annular metallic core member fit around the inboard end of the outer member. A sensor unit incorporated with a magnetic sensor is mounted on the sensor holding portion so as to protrude toward the inboard side from the core member. An output cable extends outward from the circumferential end face of the sensor unit in the tangential direction of the arcuate sensor holding portion so as to take the output detected by the magnetic sensor with the output cable through a narrow space on the inboard side (e.g. Patent Document 1).
In the device described in Patent Document 1, the magnetic encoder on the inner member is mounted on the outer face of an annular portion of a slinger mounted on the inboard side of the inner member to seal the bearing space, and the magnetic sensor is mounted in the sensor unit so as to axially oppose to the magnetic encoder. In many cases, a circuit board for processing the output detected by the magnetic sensor is mounted together in the sensor unit. In this case, the output cable is connected to the magnetic sensor through the circuit board. Materials such as hall element, hall IC and MR element are used for the magnetic sensor.
Patent Document 1: Japanese Patent No. 3231185